Hi Marius,
When you hit Estop do the drives power down completely? If so, you might
as well stick with step/dir without encoder feedback. With step/dir the
only thing encoder feedback will do for you is let you track the
machine's movement when it is in estop. If the drives power down you
lose that advantage.
For instance the SGDA drives on my Hurco are powered just from 220V AC.
If I hit Estop that 220V goes away and the machine has no way of
tracking it's movement. It then needs to be re-homed when taken out of
estop. Some drives have a separate logic supply that keeps the encoders
powered even in Estop. Both my router and lathe are set up that way so
you only need to home once when you first power the machine up for the day.
For safety reasons I prefer to leave machines in estop if they are going
to be left unused for more than a few minutes. This makes the Hurco a
bit tedious as I often need to re-home.
Les
On 04/12/2019 19:16, Marius wrote:
Hi Les
Thanks for the feedback. I agree with using the analog option but in
this case the motors are already tuned and wired. As long as I have
the encoder feedback, I am sure that the system will be accurate
enough (I hope)
I dont have a lot of time to do the conversion in so I might have to
use the STEP/DIR option. The machine is working fine now but for the
hand held (Chinese) controller that is erratic to say the least.
On 2019/12/04 13:51, Les Newell wrote:
Hi Marius,
If I was doing it I'd go with a 7I97 and use analog control for the
drives. My Hurco mill uses older SGDA08 drives and I use analog
control in torque mode. I used to run the drives in velocity mode but
I found I got better accuracy in torque mode with no dithering at
rest. With velocity mode you always end up with the drive hunting
between encoder counts when at rest.
The only advantage of using a 7I95 is that you can use the existing
drive tuning so you don't need to worry about setting up the PID
loops. You'll probably get better accuracy with analog control but
for a router the difference is probably too small to have a
measurable effect on your final parts.
Les
On 04/12/2019 09:31, Marius wrote:
Hi
I have been requested to convert a router that has Yaskawa Servo
Packs (SGD7S with analog and step/dir and encoders) already
installed. The installation makes use of the STEP/DIR signals
currently but with no encoder feedback.
I intend to use the Mesa 7I95 to replace the Chinese controller. My
question is: Is it ok to use the STEP/DIR feature of this servo pack
with encoder feedback to LCNC or should I go the Analog route and
redo the complete system making use of the 7I97.
Regards
Marius
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